This falls under geometry. The two labeled angles are congruent, which means the line segment between them (AD in the image) is a bisector of the angle at vertex A. Use the angle bisector theorem, which says that




Let x= 2.3181818...
then
10x=23.181818... and
1,000x=2,318.1818...
1,000x-10x=2,318.1818...-23.181818...
990x = 2,318 - 23
990x = 2295
x=2295/990
dividing by 5 both numerator and denominator:
x= 459/198
now, x= 198 + 198+ 63
so

Answer:
Cable company marked up monthly cost by 6% .New cost = $63.6
cost before increase = 63.6 × 100/106
= $60